Imaging lens

ABSTRACT

An imaging lens including, from an object side, a diaphragm, a first lens that is a lens having a positive power whose convex surface faces the object side, and a second lens having a negative power whose concave surface faces the object side, wherein a condition expressed by the following expressions is to be satisfied: −0.1.≦r 1 /r 2 &lt;0.1, 0.85≦f 1 /FL≦1, and 0.1≦d 3 /FL≦0.3 (where, r 1 : center radius curvature of the object side face of the first lens, r 2 : center radius curvature of the image surface side face of the first lens, f 1 : focal distance of the first lens, d 3 : center thickness of the second lens and FL: focal distance of the entire lens system).

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an imaging lens. In particular, the present invention relates to an imaging lens of a two-lens structure that is capable of reducing size and weight and enhancing optical performance. The imaging lens is used for an image-taking device that forms an image of an object, such as scenery or a human figures, on an image-taking surface of a solid image pickup element such as a CCD, CMOS, etc. The solid image pickup element is mounted on a portable computer, a television phone, a portable phone, and the like.

2. Description of the Related Art

Recently, there has been an increasing demand for cameras that utilize a solid image pickup element, such as a CCD, CMOS, or the like, which is mounted on a portable phone, a portable computer, and a television phone, for example. It is demanded that a camera such as this is small and light because the camera is required to be mounted on a limited installation space.

Further, in recent years, there has been an increasing demand for a high-optical-performance lens system capable of sufficiently utilizing resolution capabilities of solid image pickup elements having a high resolution exceeding one million pixels. Achieving a balance between size and weight reduction and improvement in optical performance is becoming increasingly important.

From this perspective, a two-lens structure lens system that is smaller and lighter than a three-lens structure lens system and superior to a single-lens structure lens system in optical performance is advantageous. Lens systems, such as those described in Patent Literatures 1 and 2, have been proposed as such two-lens structure lens systems.

[Patent Literature 1] Japanese Patent Unexamined Publication No. 2004-177628 (Especially, see SECOND EXAMPLE)

[Patent Literature 2] Japanese Patent Unexamined Publication No. 2004-170883 (Especially, see SECOND EXAMPLE)

[Patent Literature 3] Japanese Patent Unexamined Publication No. 2004-170460

DISCLOSURE OF THE INVENTION Problems to be Solved the Invention

However, the lens systems described in Patent Literature 1 and Patent Literature 2 are both disadvantageous in that a second lens is a lens having positive power, and effective aberration correction through combination of powers of a first lens and the second lens is difficult to achieve.

In addition, the lens system described in Patent Literature 3 is disadvantageous in that size and weight reduction is difficult to achieve because power distribution on a first face of the first lens is not optimal.

The present invention has been achieved in light of the above-described problems. An object of the invention is to provide an imaging lens having improved optical performance while being reduced in size and weight.

SUMMARY OF THE INVENTION

In order to achieve the aforementioned object, an imaging lens according to a first aspect of the present invention is an imaging lens used for forming an image of an object on an image-taking surface of a solid image pickup element comprising, in order from an object side to an image surface side: a diaphragm, a first lens that is a lens having a positive power whose convex surface faces the object side, and a second lens that is a lens having a negative power whose concave surface faces the object side, wherein a condition expressed by the following expressions (1) to (3) are to be satisfied: 0.1≦r ₁ /r ₂<0.1  (1) 0.85≦f ₁ /FL≦1  (2) 0.1≦d ₃ /FL≦0.3  (3) where,

r₁: center radius curvature of the object side face of the first lens

r₂: center radius curvature of the image surface side face of the first lens

f₁: focal distance of the first lens

d₃: center thickness of the second lens

FL: focal distance of the entire lens system.

In the invention, when the diaphragm is disposed closest to the object side, positioning of the diaphragm in a same position in an optical axis direction as a point on the optical axis (referred to, hereinafter, as a surface apex) of a surface (convex surface) of the first lens on the object side cannot be avoided. In addition, the surface apex and surrounding area of the surface of the first lens on the object side passing through the diaphragm and being positioned (projecting) closer to the object side than the diaphragm cannot be avoided. Even in this instance, because the diaphragm is physically positioned closer to the object side than the overall first lens, the configuration does not depart from the description in the scope of claims. To reduce the size of the optical system, the diaphragm is preferably positioned closer to the image surface side than the surface apex of the surface of the first lens on the object side.

In the first aspect of the invention, the diaphragm is disposed closest to the object side. The first lens is a positive lens that is convex on the object side. The second lens is a negative lens whose concave surface faces the object side. In addition, the condition expressed by the expressions (1) to (3) is satisfied. Therefore, optical performance and productivity can be improved while achieving size and weight reduction.

Productivity, herein, means not only the productivity for mass-producing the imaging lens (such as moldability and cost when the imaging lens is mass-produced by injection molding), but also easiness of processing, manufacture, etc. of equipment used for manufacturing the imaging lens (such as easiness of processing a mold used for injection molding) (the same applies hereinafter).

In an imaging lens according to a second aspect is the imaging lens according to the first aspect, wherein, further, a condition expressed by a following expression (4) is further satisfied: 0.45≦r ₁ /FL≦0.53  (4)

In the second aspect of the invention, the expression (4) is further satisfied. Therefore, further excellent balance can be achieved among size and weight reduction, improvement in optical performance, and improvement in productivity.

In an imaging lens according to a third aspect is the imaging lens according to the first aspect, wherein, further, a condition expressed by a following expression (5) is further satisfied: 0.65≦d ₂ /d ₁≦1.25  (5) where,

d₁: center thickness of the first lens

d₂: distance between the first lens and the second lens on the optical axis.

In the third aspect of the invention, the expression (5) is further satisfied. Therefore, a means for effectively blocking unnecessary light can be appropriately employed while maintaining productivity.

In an imaging lens according to a fourth aspect is the imaging lens according to the first aspect, wherein, further, a condition expressed by a following expression (6) is further satisfied: 0.65≦d ₂ /d ₃≦1.1  (6) where,

d₂: distance between the first lens and the second lens on the optical axis.

In the fourth aspect of the invention, the expression (6) is further satisfied. Therefore, a means for effectively blocking unnecessary light can be appropriately employed while maintaining productivity.

In an imaging lens according to a fifth aspect is the imaging lens according to the first aspect, wherein, further, a condition expressed by a following expression (7) is further satisfied: 0.1≦d ₁ /FL≦0.3  (7) where,

d₁: center thickness of the first lens.

In the fifth aspect of the invention, the expression (7) is further satisfied. Therefore, further excellent balance can be achieved between size and weight reduction and maintenance of productivity.

In an imaging lens according to a sixth aspect is the imaging lens according to the first aspect, wherein, further, a condition expressed by a following expression (8) is further satisfied: 0.9≦L/FL≦1.2  (8) where,

L: entire length of the lens system (distance from the surface closest positioned to the object side to the image taking surface on the optical axis [air reduced length]).

In the sixth aspect of the invention, the expression (8) is further satisfied. Therefore, further excellent balance can be achieved between size and weight reduction and maintenance of productivity.

EFFECTS OF THE INVENTION

With the imaging lens according to the present invention, optical performance can be improved while achieving size and weight reduction.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram for showing an embodiment of the imaging lens according to the present invention;

FIG. 2 is a schematic diagram for showing FIRST EXAMPLE of the imaging lens according to the present invention;

FIG. 3 shows graphs for describing the astigmatism and distortion of the imaging lens shown in FIG. 2;

FIG. 4 is a schematic diagram for showing SECOND EXAMPLE of the imaging lens according to the present invention;

FIG. 5 shows graphs for describing the astigmatism and distortion of the imaging lens shown in FIG. 4;

FIG. 6 is a schematic diagram for showing THIRD EXAMPLE of the imaging lens according to the present invention;

FIG. 7 shows graphs for describing the astigmatism and distortion of the imaging lens shown in FIG. 6;

FIG. 8 is a schematic diagram for showing FOURTH EXAMPLE of the imaging lens according to the present invention;

FIG. 9 shows graphs for describing the astigmatism and distortion of the imaging lens shown in FIG. 8;

FIG. 10 is a schematic diagram for showing FIFTH EXAMPLE of the imaging lens according to the present invention;

FIG. 11 shows graphs for describing the astigmatism and distortion of the imaging lens shown in FIG. 10;

FIG. 12 is a schematic diagram for showing SIXTH EXAMPLE of the imaging lens according to the present invention;

FIG. 13 shows graphs for describing the astigmatism and distortion of the imaging lens shown in FIG. 12;

FIG. 14 is a schematic diagram for showing SEVENTH EXAMPLE of the imaging lens according to the present invention;

FIG. 15 shows graphs for describing the astigmatism and distortion of the imaging lens shown in FIG. 14;

FIG. 16 is a schematic diagram for showing EIGHTH EXAMPLE of the imaging lens according to the present invention;

FIG. 17 shows graphs for describing the astigmatism and distortion of the imaging lens shown in FIG. 16;

FIG. 18 is a schematic diagram for showing NINTH EXAMPLE of the imaging lens according to the present invention;

FIG. 19 shows graphs for describing the astigmatism and distortion of the imaging lens shown in FIG. 18;

FIG. 20 is a schematic diagram for showing TENTH EXAMPLE of the imaging lens according to the present invention;

FIG. 21 shows graphs for describing the astigmatism and distortion of the imaging lens shown in FIG. 20;

FIG. 22 is a schematic diagram for showing ELEVENTH EXAMPLE of the imaging lens according to the present invention;

FIG. 23 shows graphs for describing the astigmatism and distortion of the imaging lens shown in FIG. 22;

FIG. 24 is a schematic diagram for showing TWELFTH EXAMPLE of the imaging lens according to the present invention;

FIG. 25 shows graphs for describing the astigmatism and distortion of the imaging lens shown in FIG. 24;

FIG. 26 is a schematic diagram for showing THIRTEENTH EXAMPLE of the imaging lens according to the present invention;

FIG. 27 shows graphs for describing the astigmatism and distortion of the imaging lens shown in FIG. 26;

FIG. 28 is a schematic diagram for showing FOURTEENTH EXAMPLE of the imaging lens according to the present invention;

FIG. 29 shows graphs for describing the astigmatism and distortion of the imaging lens shown in FIG. 28;

FIG. 30 is a schematic diagram for showing FIFTEENTH EXAMPLE of the imaging lens according to the present invention;

FIG. 31 shows graphs for describing the astigmatism and distortion of the imaging lens shown in FIG. 30;

FIG. 32 is a schematic diagram for showing SIXTEENTH EXAMPLE of the imaging lens according to the present invention;

FIG. 33 shows graphs for describing the astigmatism and distortion of the imaging lens shown in FIG. 32;

FIG. 34 is a schematic diagram for showing SEVENTEENTH EXAMPLE of the imaging lens according to the present invention;

FIG. 35 shows graphs for describing the astigmatism and distortion of the imaging lens shown in FIG. 34;

FIG. 36 is a schematic diagram for showing EIGHTEENTH EXAMPLE of the imaging lens according to the present invention;

FIG. 37 shows graphs for describing the astigmatism and distortion of the imaging lens shown in FIG. 36;

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

An embodiment of the imaging lens according to the present invention will be described hereinafter by referring to FIG. 1.

As shown in FIG. 1, an imaging lens 1 of the embodiment comprises, in order from the object side towards the image surface side, a diaphragm 2, a resin-type first lens 3 which is a lens having a positive power with its convex surface facing the object side, and a resin-type second lens 4 which is a lens having a negative power with its concave surface facing the object side.

Herein, each of the lens surfaces on the object side and the image surface side of the first lens 3 and the second lens 4 is respectively referred to as a first face and a second face.

On the second face side of the second lens 4, there are disposed an image-taking surface 5 which is a light-receiving surface of a solid image pickup element such as a CCD or a CMOS, respectively.

Various filters, such as a cover glass, an infrared (IR) cut filter, and a low-pass filter, may be disposed as required between a second face of the second lens 4 and an image-taking surface 5. The IR cut filter may be formed on any one surface such as the second face 3 b of the first lens 3 or a plurality of surfaces, among each lens face of the first lens 3 and the second lens 4.

In this way, according to the embodiment, high telecentricity can be ensured as a result of the diaphragm 2 being positioned closest to the object side. Therefore, an incidence angle of light incident on a sensor of the solid image pickup element can be relaxed.

According to the embodiment, the second lens 4 is a lens having a negative power, while the first lens 3 is a positive lens that is convex on the object side. Therefore, effective aberration correction can be achieved through combination of powers between the second lens 4 and the first lens 3.

Moreover, according to the embodiment, a condition expressed by a following expressions (1) to (3) are satisfied: −0.1≦r ₁ /r ₂<0.1  (1) 0.85≦f ₁ /FL≦1  (2) 0.1≦d ₃ /FL≦0.3  (3) where,

r₁ in the expression (1) is center radius curvature of the object side face 3 a of the first lens 3 (the same applies hereinafter). r₂ in the expression (1) is center radius curvature of the image surface side face 3 b of the first lens 3 (the same applies hereinafter). f₁ in the expression (2) is focal distance of the first lens 3 (the same applies hereinafter). d₃ in the expression (3) is center thickness of the second lens 4 (the same applies hereinafter). FL in the expressions (2) and (3) is focal distance of the entire lens system (the same applies hereinafter).

Here, when the value of r₁/r₂ is less than the value (−0.1) shown in the expression (1), aberration correction effect on a peripheral part of the second face 3 b of the first lens 3 weakens. Achieving desired optical performance, while ensuring size and weight reduction of the overall optical system, becomes difficult. On the other hand, when the value of r₁/r₂ is equal to or greater than the value (0.1) shown in the expression (1), the center radius curvatures of both a first face 3 a and the second face 3 b of the first lens 3 become too small. Manufacturing an injection-molding mold used to manufacture the first lens 3 by injection molding, while ensuring size and weight reduction of the overall optical system, becomes difficult.

Therefore, according to the embodiment, by the value of r₁/r₂ being set to satisfy the expression (1), optical performance and productivity can be improved while achieving size and weight reduction.

It is more preferable for the relation between r₁ and r₂ to satisfy an expression −0.1≦r₁/r₂≦0.05.

Here, when the value of f₁/FL is less than the value (0.85) shown in the expression (2), the power of the first lens 3 becomes too large compared to the power of the overall optical system. Therefore, achieving the desired optical performance becomes difficult. On the other hand, when the value of f₁/FL is greater than the value (1) shown in the expression (2), the power of the first lens 3 becomes too small compared to the power of the overall optical system. Size and weight reduction of the overall optical system becomes difficult to achieve.

Therefore, by the value of f₁/FL being set to satisfy the expression (2), excellent balance can be further achieved between size and weight reduction and improvement in optical performance.

It is more preferable for the relation between f₁ and FL to satisfy an expression 0.85≦f₁/FL≦0.95.

Here, when the value of d₃/FL is less than the value (0.1) shown in the expression (3), the center thickness of the second lens 4 becomes too thin. Manufacturing the second lens 4 becomes difficult when the second lens 4 is manufactured by injection molding. On the other hand, when the value of d₃/FL is greater than the value (0.3) shown in the expression (3), the center thickness of the second lens 4 becomes too thick compared to the overall length of the optical system. Size and weight reduction become difficult to achieve.

Therefore, by the value of d₃/FL being set to satisfy the expression (3), productivity can be maintained while more effectively reducing size and weight.

It is more preferable for the relation between d₃ and FL to satisfy an expression 0.15≦d₃/FL≦0.3. 0.45≦r ₁ /FL≦0.53  (4).

Here, when the value of r₁/FL is less than the value (0.45) shown in the expression (4), the center radius curvature of the first lens 3 becomes too small. Therefore, the first lens 3 becomes difficult to manufacture. On the other hand, when the value of r₁/FL is greater than the value (0.53) shown in the expression (4), the overall optical system becomes too large. Size and weight reduction becomes difficult to achieve.

Therefore, by the value of r₁/FL being set to satisfy the expression (4), excellent balance can be achieved among size and weight reduction, improvement in optical performance, and improvement in productivity.

It is more preferable for the relation between r₁ and FL to satisfy an expression 0.48<r₁/FL≦0.52.

According to a more preferable embodiment, a condition expressed by a following expression (5) is satisfied: 0.65≦d ₂ /d ₁≦1.25  (5) where,

d₁ in the expression (5) is center thickness of the first lens 3 (the same applies hereinafter). d2 in the expression (5) is distance between the first lens 3 and the second lens 4 on the optical axis 6 (the same applies hereinafter).

Here, when the value of d₂/d₁ is less than the value (0.65) shown in the expression (5), the distance between the first lens 3 and the second lens 4 becomes too narrow. Inserting a blocking shield or the like between the first lens 3 and the second lens 4 to effectively block unnecessary light becomes difficult. In addition, edge sections of respective optical surfaces of the first lens 3 and the second lens 4 become too close to each other, thereby increasing generation of unnecessary light. On the other hand, when the value of d₂/d₁ is greater than the value (1.25) shown in the expression (5), the center thickness of the first lens 3 becomes too thin. Manufacturing the first lens 3 becomes difficult when the first lens 3 is manufactured by injection molding.

Therefore, by the value of d₂/d₁ being set to satisfy the expression (5), a means for effectively blocking unnecessary light can be appropriately employed while maintaining productivity.

It is more preferable for the relation between d₁ and d₂ to satisfy an expression 0.65≦d₂/d₁≦1.2.

According to a more preferable embodiment, a condition expressed by a following expression (6) is satisfied: 0.65≦d ₂ /d ₃≦1.1  (6).

Here, when the value of d₂/d₃ is less than the value (0.65) shown in the expression (6), the distance between the first lens 3 and the second lens 4 becomes too narrow. Inserting a blocking shield or the like between the first lens 3 and the second lens 4 to effectively block unnecessary light becomes difficult. In addition, the edge sections of respective optical surfaces of the first lens 3 and the second lens 4 become too close to each other, thereby increasing generation of unnecessary light. On the other hand, when the value of d₂/d₃ is greater than the value (1.1) shown in the expression (6), the center thickness of the second lens 4 becomes too thin. Manufacturing the second lens 4 becomes difficult when the second lens 4 is manufactured by injection molding.

Therefore, by the value of d₂/d₃ being set to satisfy the expression (6), a means for effectively blocking unnecessary light can be appropriately employed while maintaining productivity.

It is more preferable for the relation between d₂ and d₃ to satisfy an expression 0.65≦d₂/d₃≦1.

According to a more preferable embodiment, a condition expressed by a following expression (7) is satisfied: 0.1≦d ₁ /FL≦0.3  (7).

Here, when the value of d₁/FL is less than the value (0.1) shown in the expression (7), the center thickness of the first lens 3 becomes too thin. Manufacturing the first lens 3 becomes difficult when the first lens 3 is manufactured by injection molding. On the other hand, when the value of d₁/FL is greater than the value (0.3) shown in the expression (7), the center thickness of the first lens 3 becomes too thick compared to the overall length of the optical system. Size and weight reduction become difficult to achieve.

Therefore, by the value of d₁/FL being set to satisfy the expression (7), excellent balance can be further achieved between size and weight reduction and maintenance of productivity.

It is more preferable for the relation between d₁ and FL to satisfy an expression 0.15≦d₁/FL≦0.3.

According to a more preferable embodiment, a condition expressed by a following expression (8) is satisfied: 0.9≦L/FL≦1.2  (8) where, L in the expression (8) is entire length of the lens system, in other words, distance from the surface positioned closest to the object side to the image taking surface 5 on the optical axis 6 [air reduced length] (the same applies hereinafter).

Here, when the value of L/FL is less than the value (0.9) shown in the expression (8), the overall length of the optical system becomes too short. Productivity during an assembly process of each of the lenses 3 and 4 deteriorates. On the other hand, when the value of L/FL is greater than the value (1.2) shown in the expression (8), the overall length of the optical system becomes too long. Mounting in a small camera of a mobile phone or the like becomes difficult.

Therefore, by the value of L/FL being set to satisfy the expression (8), balance can be more effectively achieved between size and weight reduction and maintenance of productivity.

It is more preferable for the relation between L and FL to satisfy an expression 0.95≦L/FL≦1.2.

Moreover, examples of a resin material used for molding the first lens 3 and the second lens 4 may be materials of various compositions with transparency, such as acrylic, polycarbonate, amorphous polyolefin resin, etc. However, from the perspective of further improving the manufacturing efficiency and further reducing the manufacturing costs, it is preferable that the resin materials of both lenses 3 and 4 are unified and are the same resin material.

EXAMPLES

Next, EXAMPLES of the present invention will be described by referring to FIG. 2 to FIG. 37.

In the EXAMPLES, Fno denotes F number and r denotes the curvature radius of the optical surface (the center radius curvature in the case of a lens). Further, d denotes a distance to the next optical surface on the optical axis 6, nd denotes the index of refraction when the d line (yellow) is irradiated, and νd denotes the Abbe number of each optical system also when the d line is irradiated.

k, A, B, C, and D denote each coefficient in a following expression (9). Specifically, the shape of the aspherical surface of the lens is expressed by the following expression provided that the direction of the optical axis 6 is taken as the Z axis, the direction orthogonal to the optical axis 6 is taken as the X axis, the traveling direction of light is positive, k is the constant of cone, A, B, C, and D are the aspherical coefficients, and r is the curvature radius. Z(X)=r− ¹ X ²/[1+{1−(k+1)r− ² X ²}^(1/2) ]+AX ⁴ +BX ⁶ +CX ⁸ +DX ¹⁰  (9)

In the following EXAMPLES, reference code E used for a numerical value denoting the constant of cone and the aspherical coefficient indicates that the numerical value following E is an exponent having 10 as the base and that the numerical value before E is multiplied by the numerical value denoted by the exponent having 10 as the base. For example, −8.03E+2 denotes −8.03×10².

First Example

FIG. 2 shows a FIRST EXAMPLE of the present invention. The lens 1 in the FIRST EXAMPLE is identical with the lens 1 whose composition is shown in FIG. 1. In the FIRST EXAMPLE, a surface apex (a point intersecting with an optical axis 6) and surrounding area of a first face 3 a of the first lens 3 passes through the diaphragm 2 and is positioned closest to the object side.

The imaging lens 1 of the FIRST EXAMPLE was set under the following condition.

Lens Data L = 1.89 mm, FL = 1.648 mm, f₁ = 1.434 mm, f₂ = −6.332 mm, Fno = 2.8 Face Number r D nd νd (Object Point) 1(Diaphragm) ∞ −0.045 2(First Face of First Lens) 0.825 0.450 1.531 56.0 3(Second Face of First Lens) −8.500 0.330 4(First Face of Second Lens) −3.500 0.450 1.531 56.0 5(Second Face of Second Lens) 100.000 (Image Surface) Face Number k A B C D 2 0 −1.27 3.59E+1 −8.03E+2 8.16E+3 3 0 −11.10 −1.13E+1 6.03E+1 −1.37E+2 4 0 −1.10 −7.05E+1 1.18E+3 −1.24E+4 5 0 −1.59E−1 −9.45 5.97E+1 −2.10E+2

Under such conditions, r₁/r₂=−0.097 was achieved, thereby satisfying the expression (1). f₁/FL=0.870 was achieved, thereby satisfying the expression (2). d₃/FL=0.27 was achieved, thereby satisfying the expression (3). r₁/FL=0.501 was achieved, thereby satisfying the expression (4). d₂/d₁=0.73 was achieved, thereby satisfying the expression (5). d₂/d₃=0.73 was achieved, thereby satisfying the expression (6). d₁/FL=0.27 was achieved, thereby satisfying the expression (7). L/FL=1.147 was achieved, thereby satisfying the expression (8).

FIG. 3 shows the astigmatism and distortion of the imaging lens 1 of the FIRST EXAMPLE.

According to the result, each of the astigmatism and distortion was almost satisfied. It can be seen from the result that a sufficient optical property can be obtained.

Second Example

FIG. 4 shows a SECOND EXAMPLE of the present invention. In the SECOND EXAMPLE, a surface apex and surrounding area of a first face 3 a of the first lens 3 passes through the diaphragm 2 and is positioned closest to the object side.

The imaging lens 1 of the SECOND EXAMPLE was set under the following condition.

Lens Data L = 1.9 mm, FL = 1.626 mm, f₁ = 1.464 mm, f₂ = −9.471 mm, Fno = 2.8 Face Number r d nd νd (Object Point) 1(Diaphragm) ∞ −0.045 2(First Face of First Lens) 0.833 0.450 1.531 56.0 3(Second Face of First Lens) −10.000 0.320 4(First Face of Second Lens) −4.000 0.460 1.531 56.0 5(Second Face of Second Lens) −20.000 (Image Surface) Face Number k A B C D 2 0 −1.28 3.68E+1 −8.15E+2 8.31E+3 3 0 −1.04 −1.02E+1 1.57E+1 4.64E+2 4 0 −1.05 −6.67E+1 1.19E+3 −1.28E+4 5 0 −3.75E−1 −5.61 3.58E+1 −1.27E+2

Under such conditions, r₁/r₂=−0.083 was achieved, thereby satisfying the expression (1). f₁/FL=0.900 was achieved, thereby satisfying the expression (2). d₃/FL=0.28 was achieved, thereby satisfying the expression (3). r₁/FL=0.512 was achieved, thereby satisfying the expression (4). d₂/d₁=0.71 was achieved, thereby satisfying the expression (5). d₂/d₃=0.70 was achieved, thereby satisfying the expression (6). d₁/FL=0.28 was achieved, thereby satisfying the expression (7). L/FL=1.169 was achieved, thereby satisfying the expression (8).

FIG. 5 shows the astigmatism and distortion of the imaging lens 1 of the SECOND EXAMPLE.

According to the result, each of the astigmatism and distortion was almost satisfied. It can be seen from the result that a sufficient optical property can be obtained.

Third Example

FIG. 6 shows a THIRD EXAMPLE of the present invention. In the THIRD EXAMPLE, a surface apex and surrounding area of a first face 3 a of the first lens 3 passes through the diaphragm 2 and is positioned closest to the object side, under the following condition.

Lens Data L = 1.89 mm, FL = 1.626 mm, f₁ = 1.474 mm, f₂ = −9.376 mm, Fno = 2.8 Face Number r d nd νd (Object Point) 1(Diaphragm) ∞ −0.030 2(First Face of First Lens) 0.830 0.450 1.531 56.0 3(Second Face of First Lens) −12.000 0.320 4(First Face of Second Lens) −5.000 0.440 1.531 56.0 5(Second Face of Second Lens) 0.000 (Image Surface) Face Number k A B C D 2 0 −1.20 3.39E+1 −7.82E+2 8.15E+3 3 0 −1.18 −1.11E+1 5.14E+1 7.14 4 0 −1.28 −6.13E+1 1.02E+3 −1.11E+4 5 0 −4.96E−2 −1.12E+1 7.32E+1 −2.76E+2

Under such conditions, r₁/r₂=−0.069 was achieved, thereby satisfying the expression (1). f₁/FL=0.907 was achieved, thereby satisfying the expression (2). d₃/FL=0.27 was achieved, thereby satisfying the expression (3). r₁/FL=0.510 was achieved, thereby satisfying the expression (4). d₂/d₁=0.71 was achieved, thereby satisfying the expression (5). d₂/d₃=0.73 was achieved, thereby satisfying the expression (6). d₁/FL=0.28 was achieved, thereby satisfying the expression (7). L/FL=1.162 was achieved, thereby satisfying the expression (8).

FIG. 7 shows the astigmatism and distortion of the imaging lens 1 of the THIRD EXAMPLE.

According to the result, each of the astigmatism and distortion was almost satisfied. It can be seen from the result that a sufficient optical property can be obtained.

Fourth Example

FIG. 8 shows a FOURTH EXAMPLE of the present invention. In the FOURTH EXAMPLE, a surface apex and surrounding area of a first face 3 a of the first lens 3 passes through the diaphragm 2 and is positioned closest to the object side.

The imaging lens 1 of the FOURTH EXAMPLE was set under the following condition.

Lens Data L = 1.92 mm, FL = 1.6649 mm, f₁ = 1.492 mm, f₂ = −7.752 mm, Fno = 2.8 Face Number r d nd νd (Object Point) 1(Diaphragm) ∞ −0.045 2(First Face of First Lens) 0.8333 0.450 1.531 56.0 3(Second Face of First Lens) −14.2900 0.320 4(First Face of Second Lens) −5.8820 0.460 1.531 56.0 5(Second Face of Second Lens) 14.2860 (Image Surface) Face Number k A B C D 2 0 −1.32 3.74E+1 −8.11E+2 8.11E+3 3 0 −1.10 −9.22 1.09E+1 4.42E+2 4 0 −1.04 −6.68E+1 1.20E+3 −1.30E+4 5 0 −4.92E−1 −4.73 3.26E+1 −1.24E+2

Under such conditions, r₁/r₂=−0.058 was achieved, thereby satisfying the expression (1). f₁/FL=0.896 was achieved, thereby satisfying the expression (2). d₃/FL=0.28 was achieved, thereby satisfying the expression (3). r₁/FL=0.501 was achieved, thereby satisfying the expression (4). d₂/d₁=0.71 was achieved, thereby satisfying the expression (5). d₂/d₃=0.70 was achieved, thereby satisfying the expression (6). d₁/FL=0.27 was achieved, thereby satisfying the expression (7). L/FL=1.153 was achieved, thereby satisfying the expression (8).

FIG. 9 shows the astigmatism and distortion of the imaging lens 1 of the FOURTH EXAMPLE.

According to the result, each of the astigmatism and distortion was almost satisfied. It can be seen from the result that a sufficient optical property can be obtained.

Fifth Example

FIG. 10 shows a FIFTH EXAMPLE of the present invention. In the FIFTH EXAMPLE, a surface apex and surrounding area of a first face 3 a of the first lens 3 passes through the diaphragm 2 and is positioned closest to the object side.

The imaging lens 1 of the FIFTH EXAMPLE was set under the following condition.

Lens Data L = 1.90 mm, FL = 1.629 mm, f₁ = 1.506 mm, f₂ = −12.26 mm, Fno = 2.8 Face Number r d nd νd (Object Point) 1(Diaphragm) ∞ −0.030 2(First Face of First Lens) 0.830 0.450 1.531 56.0 3(Second Face of First Lens) −20.000 0.320 4(First Face of Second Lens) −6.000 0.450 1.531 56.0 5(Second Face of Second Lens) −75.000 (Image Surface) Face Number k A B C D 2 0 −1.12 3.24E+1 −7.91E+2 8.72E+3 3 0 −1.14 −1.02E+1 3.48E+1 8.27E+1 4 0 −1.32 −5.22E+1 8.55E+2 −9.64E+3 5 0 −1.83E−1 −7.12 3.71E+1 −1.19E+2

Under such conditions, r₁/r₂=−0.042 was achieved, thereby satisfying the expression (1). f₁/FL=0.924 was achieved, thereby satisfying the expression (2). d₃/FL=0.28 was achieved, thereby satisfying the expression (3). r₁/FL=0.510 was achieved, thereby satisfying the expression (4). d₂/d₁=0.71 was achieved, thereby satisfying the expression (5). d₂/d₃=0.71 was achieved, thereby satisfying the expression (6). d₁/FL=0.28 was achieved, thereby satisfying the expression (7). L/FL=1.166 was achieved, thereby satisfying the expression (8).

FIG. 11 shows the astigmatism and distortion of the imaging lens 1 of the FIFTH EXAMPLE.

According to the result, each of the astigmatism and distortion was almost satisfied. It can be seen from the result that a sufficient optical property can be obtained.

Sixth Example

FIG. 12 shows a SIXTH EXAMPLE of the present invention. In the SIXTH EXAMPLE, a surface apex and surrounding area of a first face 3 a of the first lens 3 passes through the diaphragm 2 and is positioned closest to the object side.

The imaging lens 1 of the SIXTH EXAMPLE was set under the following condition.

Lens Data L = 1.32 mm, FL = 1.156 mm, f₁ = 1.032 mm, f₂ = −5.317 mm, Fno = 2.8 Face Number r d nd νd (Object Point) 1(Diaphragm) ∞ −0.030 2(First Face of First Lens) 0.556 0.300 1.531 56.0 3(Second Face of First Lens) −50.000 0.215 4(First Face of Second Lens) −4.000 0.310 1.531 56.0 5(Second Face of Second Lens) 10.000 (Image Surface) Face Number k A B C D 2 0 −4.00 2.23E+2 −9.55E+3 1.98E+5 3 0 −2.97 −6.10E+1 −1.47E+2 1.82E+4 4 0 −2.94 −4.45E+2 1.67E+4 −3.97E+5 5 0 −2.22 −1.63 −8.94E+1 1.43E+3

Under such conditions, r₁/r₂=−0.011 was achieved, thereby satisfying the expression (1). f₁/FL=0.893 was achieved, thereby satisfying the expression (2). d₃/FL=0.27 was achieved, thereby satisfying the expression (3). r₁/FL=0.481 was achieved, thereby satisfying the expression (4). d₂/d₁=0.72 was achieved, thereby satisfying the expression (5). d₂/d₃=0.69 was achieved, thereby satisfying the expression (6). d₁/FL=0.26 was achieved, thereby satisfying the expression (7). L/FL=1.142 was achieved, thereby satisfying the expression (8).

FIG. 13 shows the astigmatism and distortion of the imaging lens 1 of the SIXTH EXAMPLE.

According to the result, each of the astigmatism and distortion was almost satisfied. It can be seen from the result that a sufficient optical property can be obtained.

Seventh Example

FIG. 14 shows a SEVENTH EXAMPLE of the present invention. In the SEVENTH EXAMPLE, a surface apex and surrounding area of a first face 3 a of the first lens 3 passes through the diaphragm 2 and is positioned closest to the object side.

The imaging lens 1 of the SEVENTH EXAMPLE was set under the following condition.

Lens Data L = 1.26 mm, FL = 1.081 mm, f1 = 1.006 mm, f2 = −10.26 mm, Fno = 2.8 Face Number r d nd νd (Object Point) 1(Diaphragm) ∞ −0.030 2(First Face of First Lens) 0.540 0.300 1.531 56.0 3(Second Face of First Lens) −70.000 0.215 4(First Face of Second Lens) −3.500 0.300 1.531 56.0 5(Second Face of Second Lens) −10.000 (Image Surface) Face Number k A B C D 2 0 −4.58 2.66E+2 −1.07E+4 2.10E+5 3 0 −2.11 −9.48E+1 9.68E+2 4.91E+3 4 0 4.05E−1 −6.01E+2 2.03E+4 −4.26E+5 5 0 −1.22 −1.04E+1 −1.33E+2 2.66E+3

Under such conditions, r₁/r₂=−0.0077 was achieved, thereby satisfying the expression (1). f₁/FL=0.931 was achieved, thereby satisfying the expression (2). d₃/FL=0.28 was achieved, thereby satisfying the expression (3). r₁/FL=0.500 was achieved, thereby satisfying the expression (4). d₂/d₁=0.72 was achieved, thereby satisfying the expression (5). d₂/d₃=0.72 was achieved, thereby satisfying the expression (6). d₁/FL=0.28 was achieved, thereby satisfying the expression (7). L/FL=1.166 was achieved, thereby satisfying the expression (8).

FIG. 15 shows the astigmatism and distortion of the imaging lens 1 of the SEVENTH EXAMPLE.

According to the result, each of the astigmatism and distortion was almost satisfied. It can be seen from the result that a sufficient optical property can be obtained.

Eighth Example

FIG. 16 shows a EIGHTH EXAMPLE of the present invention. In the EIGHTH EXAMPLE, a surface apex and surrounding area of a first face 3 a of the first lens 3 passes through the diaphragm 2 and is positioned closest to the object side.

The imaging lens 1 of the EIGHTH EXAMPLE was set under the following condition.

Lens Data L = 1.69 mm, FL = 1.482 mm, f₁ = 1.331 mm, f₂ = −7.782 mm, Fno = 2.8 Face Number r d nd Nd (Object Point) 1(Diaphragm) ∞ −0.030 2(First Face of First Lens) 0.710 0.390 1.531 56.0 3(Second Face of First Lens) 0.000 0.285 4(First Face of Second Lens) −4.150 0.370 1.531 56.0 5(Second Face of Second Lens) 0.000 (Image Surface) Face Number k A B C D 2 0 −1.82 6.63E+1 −1.89E+3 2.62E+4 3 0 −1.39 −1.63E+1 −7.34E+1 2.77E+3 4 0 −1.21 −1.41E+2 3.35E+3 −5.18E+4 5 0 −8.59E−1 −3.12 −7.52 1.59E+2

Under such conditions, r₁/r₂=0 was achieved, thereby satisfying the expression (1). f₁/FL=0.898 was achieved, thereby satisfying the expression (2). d₃/FL=0.25 was achieved, thereby satisfying the expression (3). r₁/FL=0.479 was achieved, thereby satisfying the expression (4). d₂/d₁=0.73 was achieved, thereby satisfying the expression (5). d₂/d₃=0.77 was achieved, thereby satisfying the expression (6). d₁/FL=0.26 was achieved, thereby satisfying the expression (7). L/FL=1.140 was achieved, thereby satisfying the expression (8).

FIG. 17 shows the astigmatism and distortion of the imaging lens 1 of the EIGHTH EXAMPLE.

According to the result, each of the astigmatism and distortion was almost satisfied. It can be seen from the result that a sufficient optical property can be obtained.

Ninth Example

FIG. 18 shows a NINTH EXAMPLE of the present invention. In the NINTH EXAMPLE, a surface apex and surrounding area of a first face 3 a of the first lens 3 passes through the diaphragm 2 and is positioned closest to the object side.

The imaging lens 1 of the NINTH EXAMPLE was set under the following condition.

Lens Data L = 1.67 mm, FL = 1.463 mm, f₁ = 1.316 mm, f₂ = −7.889 mm, Fno = 2.8 Face Number r d nd νd (Object Point) 1(Diaphragm) ∞ −0.030 2(First Face of First Lens) 0.700 0.380 1.531 56.0 3(Second Face of First Lens) 250.000 0.265 4(First Face of Second Lens) −4.300 0.390 1.531 56.0 5(Second Face of Second Lens) 200.000 (Image Surface) Face Number k A B C D 2 0 −1.79 5.63E+1 −1.52E+3 2.02E+4 3 0 −1.41 −2.35E+1 3.59E+1 1.62E+3 4 0 −9.44E−1 −1.52E+2 3.33E+3 −4.57E+4 5 0 −7.54E−1 −2.66 −1.39E+1 2.03E+2

Under such conditions, r₁/r₂=0.003 was achieved, thereby satisfying the expression (1). f₁/FL=0.900 was achieved, thereby satisfying the expression (2). d₃/FL=0.27 was achieved, thereby satisfying the expression (3). r₁/FL=0.478 was achieved, thereby satisfying the expression (4). d₂/d₁=0.70 was achieved, thereby satisfying the expression (5). d₂/d₃=0.68 was achieved, thereby satisfying the expression (6). d₁/FL=0.26 was achieved, thereby satisfying the expression (7). L/FL=1.141 was achieved, thereby satisfying the expression (8).

FIG. 19 shows the astigmatism and distortion of the imaging lens 1 of the NINTH EXAMPLE.

According to the result, each of the astigmatism and distortion was almost satisfied. It can be seen from the result that a sufficient optical property can be obtained.

Tenth Example

FIG. 20 shows a TENTH EXAMPLE of the present invention. In the TENTH EXAMPLE, a surface apex and surrounding area of a first face 3 a of the first lens 3 passes through the diaphragm 2 and is positioned closest to the object side.

The imaging lens 1 of the TENTH EXAMPLE was set under the following condition.

Lens Data L = 1.67 mm, FL = 1.45 mm, f₁ = 1.32 mm, f₂ = −9.301 mm, Fno = 2.8 Face Number R d nd νd (Object Point) 1(Diaphragm) ∞ −0.030 2(First Face of First Lens) 0.700 0.380 1.531 56.0 3(Second Face of First Lens) 100.000 0.265 4(First Face of Second Lens) −4.500 0.390 1.531 56.0 5(Second Face of Second Lens) −50.000 (Image Surface) Face Number k A B C D 2 0 −1.81 5.75E+1 −1.53E+3 2.03E+4 3 0 −1.37 −2.26E+1 3.20E+1 1.60E+3 4 0 −9.48E−1 −1.47E+2 3.25E+3 −4.51E+4 5 0 −7.77E−1 −1.74 −1.97E+1 2.18E+2

Under such conditions, r₁/r₂=0.007 was achieved, thereby satisfying the expression (1). f₁/FL=0.910 was achieved, thereby satisfying the expression (2). d₃/FL=0.27 was achieved, thereby satisfying the expression (3). r₁/FL=0.483 was achieved, thereby satisfying the expression (4). d₂/d₁=0.70 was achieved, thereby satisfying the expression (5). d₂/d₃=0.68 was achieved, thereby satisfying the expression (6). d₁/FL=0.26 was achieved, thereby satisfying the expression (7). L/FL=1.152 was achieved, thereby satisfying the expression (8).

FIG. 21 shows the astigmatism and distortion of the imaging lens 1 of the TENTH EXAMPLE.

According to the result, each of the astigmatism and distortion was almost satisfied. It can be seen from the result that a sufficient optical property can be obtained.

Eleventh Example

FIG. 22 shows a ELEVENTH EXAMPLE of the present invention. In the ELEVENTH EXAMPLE, a surface apex and surrounding area of a first face 3 a of the first lens 3 passes through the diaphragm 2 and is positioned closest to the object side.

The imaging lens 1 of the ELEVENTH EXAMPLE was set under the following condition.

Lens Data L = 1.68 mm, FL = 1.472 mm, f₁ = 1.328 mm, f₂ = −8.439 mm, Fno = 2.8 Face Number r d nd νd (Object Point) 1(Diaphragm) ∞ −0.030 2(First Face of First Lens) 0.700 0.380 1.531 56.0 3(Second Face of First Lens) 50.000 0.250 4(First Face of Second Lens) −4.500 0.370 1.531 56.0 5(Second Face of Second Lens) 0.000 (Image Surface) Face Number k A B C D 2 0 −1.84 5.70E+1 −1.53E+3 2.02E+4 3 0 −1.62 −2.50E+1 4.11E+1 1.57E+3 4 0 −1.40 −1.48E+2 3.30E+3 −4.63E+4 5 0 −8.59E−1 −2.83 −1.01E+1 1.89E+2

Under such conditions, r₁/r₂=0.014 was achieved, thereby satisfying the expression (1). f₁/FL=0.902 was achieved, thereby satisfying the expression (2). d₃/FL=0.25 was achieved, thereby satisfying the expression (3). r₁/FL=0.476 was achieved, thereby satisfying the expression (4). d₂/d₁=0.66 was achieved, thereby satisfying the expression (5). d₂/d₃=0.68 was achieved, thereby satisfying the expression (6) d₁/FL=0.26 was achieved, thereby satisfying the expression (7). L/FL=1.141 was achieved, thereby satisfying the expression (8).

FIG. 23 shows the astigmatism and distortion of the imaging lens 1 of the ELEVENTH EXAMPLE.

According to the result, each of the astigmatism and distortion was almost satisfied. It can be seen from the result that a sufficient optical property can be obtained.

Twelfth Example

FIG. 24 shows a TWELFTH EXAMPLE of the present invention. In the TWELFTH EXAMPLE, a surface apex and surrounding area of a first face 3 a of the first lens 3 passes through the diaphragm 2 and is positioned closest to the object side.

The imaging lens 1 of the TWELFTH EXAMPLE was set under the following condition.

Lens Data L = 1.67 mm, FL = 1.445 mm, f₁ = 1.342 mm, f₂ = −12.1 mm, Fno = 2.8 Face Number r d nd νd (Object Point) 1(Diaphragm) ∞ −0.030 2(First Face of First Lens) 0.700 0.380 1.531 56.0 3(Second Face of First Lens) 25.600 0.265 4(First Face of Second Lens) −5.700 0.400 1.531 56.0 5(Second Face of Second Lens) −50.000 (Image Surface) Face Number k A B C D 2 0 −1.81 6.26E+1 −1.66E+3 2.14E+4 3 0 −1.36 −1.68E+1 −3.74E+1 2.05E+3 4 0 −1.44 −1.18E+2 2.79E+3 −4.19E+4 5 0 −1.02 9.29E−2 −2.00E+1 1.61E+2

Under such conditions, r₁/r₂=0.027 was achieved, thereby satisfying the expression (1). f₁/FL=0.929 was achieved, thereby satisfying the expression (2). d₃/FL=0.28 was achieved, thereby satisfying the expression (3). r₁/FL=0.484 was achieved, thereby satisfying the expression (4). d₂/d₁=0.70 was achieved, thereby satisfying the expression (5). d₂/d₃=0.66 was achieved, thereby satisfying the expression (6). d₁/FL=0.26 was achieved, thereby satisfying the expression (7). L/FL=1.156 was achieved, thereby satisfying the expression (8).

FIG. 25 shows the astigmatism and distortion of the imaging lens 1 of the TWELFTH EXAMPLE.

According to the result, each of the astigmatism and distortion was almost satisfied. It can be seen from the result that a sufficient optical property can be obtained.

Thirteenth Example

FIG. 26 shows a THIRTEENTH EXAMPLE of the present invention. In the THIRTEENTH EXAMPLE, a surface apex and surrounding area of a first face 3 a of the first lens 3 passes through the diaphragm 2 and is positioned closest to the object side.

The imaging lens 1 of the THIRTEENTH EXAMPLE was set under the following condition.

Lens Data L = 1.33 mm, FL = 1.169 mm, f₁ = 1.063 mm, f₂ = −6.733 mm, Fno = 2.8 Face Number r d nd νd (Object Point) 1(Diaphragm) ∞ −0.030 2(First Face of First Lens) 0.550 0.300 1.531 56.0 3(Second Face of First Lens) 15.000 0.215 4(First Face of Second Lens) −4.400 0.310 1.531 56.0 5(Second Face of Second Lens) 20.000 (Image Surface) Face Number k A B C D 2 0 −3.76 2.11E+2 −9.26E+3 1.96E+5 3 0 −2.95 −6.11E+1 −1.13E+2 1.77E+4 4 0 −2.17 −4.64E+2 1.71E+4 −4.01E+5 5 0 −1.54 −8.17 −7.06E+1 1.50E+3

Under such conditions, r₁/r₂=0.037 was achieved, thereby satisfying the expression (1). f₁/FL=0.909 was achieved, thereby satisfying the expression (2). d₃/FL=0.27 was achieved, thereby satisfying the expression (3). r₁/FL=0.470 was achieved, thereby satisfying the expression (4). d₂/d₁=0.72 was achieved, thereby satisfying the expression (5). d₂/d₃=0.69 was achieved, thereby satisfying the expression (6). d₁/FL=0.26 was achieved, thereby satisfying the expression (7). L/FL=1.138 was achieved, thereby satisfying the expression (8).

FIG. 27 shows the astigmatism and distortion of the imaging lens 1 of the THIRTEENTH EXAMPLE.

According to the result, each of the astigmatism and distortion was almost satisfied. It can be seen from the result that a sufficient optical property can be obtained.

Fourteenth Example

FIG. 28 shows a FOURTEENTH EXAMPLE of the present invention. In the FOURTEENTH EXAMPLE, a surface apex and surrounding area of a first face 3 a of the first lens 3 passes through the diaphragm 2 and is positioned closest to the object side.

The imaging lens 1 of the FOURTEENTH EXAMPLE was set under the following condition.

Lens Data L = 1.65 mm, FL = 1.45 mm, f₁ = 1.332 mm, f₂ = −9.764 mm, Fno = 2.8 Face Number r d nd νd (Object Point) 1(Diaphragm) ∞ −0.040 2(First Face of First Lens) 0.680 0.370 1.531 56.0 3(Second Face of First Lens) 13.000 0.265 4(First Face of Second Lens) −5.500 0.380 1.531 56.0 5(Second Face of Second Lens) 100.000 (Image Surface) Face Number k A B C D 2 0 −2.10 7.86E+1 −2.18E+3 2.95E+4 3 0 −1.31 −2.46E+1 2.98E+1 2.31E+3 4 0 −5.76E−1 −1.68E+2 3.93E+3 −5.87E+4 5 0 −7.14E−1 −3.26 −1.33E+1 2.17E+2

Under such conditions, r₁/r₂=0.052 was achieved, thereby satisfying the expression (1). f₁/FL=0.919 was achieved, thereby satisfying the expression (2). d₃/FL=0.26 was achieved, thereby satisfying the expression (3) r₁/FL=0.469 was achieved, thereby satisfying the expression (4) d₂/d₁=0.72 was achieved, thereby satisfying the expression (5). d₂/d₃=0.70 was achieved, thereby satisfying the expression (6) d₁/FL=0.26 was achieved, thereby satisfying the expression (7) L/FL=1.138 was achieved, thereby satisfying the expression (8).

FIG. 29 shows the astigmatism and distortion of the imaging lens 1 of the FOURTEENTH EXAMPLE.

According to the result, each of the astigmatism and distortion was almost satisfied. It can be seen from the result that a sufficient optical property can be obtained.

Fifteenth Example

FIG. 30 shows a FIFTEENTH EXAMPLE of the present invention. In the FIFTEENTH EXAMPLE, a surface apex and surrounding area of a first face 3 a of the first lens 3 passes through the diaphragm 2 and is positioned closest to the object side.

The imaging lens 1 of the FIFTEENTH EXAMPLE was set under the following condition.

Lens Data L = 1.65 mm, FL = 1.427 mm, f1 = 1.337 mm, f2 = −14.36 mm, Fno = 2.8 Face Number r d Nd νd (Object Point) 1(Diaphragm) ∞ −0.040 2(First Face of First Lens) 0.680 0.370 1.531 56.0 3(Second Face of First Lens) 12.000 0.265 4(First Face of Second Lens) −5.500 0.380 1.531 56.0 5(Second Face of Second Lens) −20.000 (Image Surface) Face Number k A B C D 2 0 −2.10 7.91E+1 −2.18E+3 2.94E+4 3 0 −1.21 −2.46E+1 4.19E+1 2.16E+3 4 0 −3.69E−1 −1.68E+2 3.90E+3 −5.83E+4 5 0 −5.95E−1 −3.88 −1.09E+1 2.13E+2

Under such conditions, r₁/r₂=0.057 was achieved, thereby satisfying the expression (1). f₁/FL=0.937 was achieved, thereby satisfying the expression (2). d₃/FL=0.27 was achieved, thereby satisfying the expression (3). r₁/FL=0.477 was achieved, thereby satisfying the expression (4). d₂/d₁=0.72 was achieved, thereby satisfying the expression (5). d₂/d₃=0.70 was achieved, thereby satisfying the expression (6). d₁/FL=0.26 was achieved, thereby satisfying the expression (7). L/FL=1.156 was achieved, thereby satisfying the expression (8).

FIG. 31 shows the astigmatism and distortion of the imaging lens 1 of the FIFTEENTH EXAMPLE.

According to the result, each of the astigmatism and distortion was almost satisfied. It can be seen from the result that a sufficient optical property can be obtained.

Sixteenth Example

FIG. 32 shows a SIXTEENTH EXAMPLE of the present invention. In the SIXTEENTH EXAMPLE, a surface apex and surrounding area of a first face 3 a of the first lens 3 passes through the diaphragm 2 and is positioned closest to the object side.

The imaging lens 1 of the SIXTEENTH EXAMPLE was set under the following condition.

Lens Data L = 1.36 mm, FL = 1.2 mm, f₁ = 1.1 mm, f₂ = −8.067 mm, Fno = 2.8 Face Number R d nd νd (Object Point) 1(Diaphragm) ∞ −0.030 2(First Face of First Lens) 0.550 0.300 1.531 56.0 3(Second Face of First Lens) 7.100 0.210 4(First Face of Second Lens) −4.500 0.300 1.531 56.0 5(Second Face of Second Lens) 100.000 (Image Surface) Face Number k A B C D 2 0 −3.61 2.13E+2 −9.43E+3 2.00E+5 3 0 −2.90 −4.85E+1 −4.11E+2 2.10E+4 4 0 −3.69 −3.41E+2 1.40E+4 −3.71E+5 5 0 −2.36 9.52 −2.12E+2 1.89E+3

Under such conditions, r₁/r₂=0.077 was achieved, thereby satisfying the expression (1) f₁/FL=0.917 was achieved, thereby satisfying the expression (2). d₃/FL=0.25 was achieved, thereby satisfying the expression (3). r₁/FL=0.458 was achieved, thereby satisfying the expression (4). d₂/d₁=0.70 was achieved, thereby satisfying the expression (5). d₂/d₃=0.70 was achieved, thereby satisfying the expression (6). d₁/FL=0.25 was achieved, thereby satisfying the expression (7). L/FL=1.133 was achieved, thereby satisfying the expression (8).

FIG. 33 shows the astigmatism and distortion of the imaging lens 1 of the SIXTEENTH EXAMPLE.

According to the result, each of the astigmatism and distortion was almost satisfied. It can be seen from the result that a sufficient optical property can be obtained.

Seventeenth Example

FIG. 34 shows a SEVENTEENTH EXAMPLE of the present invention. In the SEVENTEENTH EXAMPLE, a surface apex and surrounding area of a first face 3 a of the first lens 3 passes through the diaphragm 2 and is positioned closest to the object side.

The imaging lens 1 of the SEVENTEENTH EXAMPLE was set under the following condition.

Lens Data L = 1.37 mm, FL = 1.21 mm, f₁ = 1.112 mm, f₂ = −8.334 mm, Fno = 2.8 Face Number R d nd νd (Object Point) 1(Diaphragm) ∞ −0.030 2(First Face of First Lens) 0.5556 0.300 1.531 56.0 3(Second Face of First Lens) 7.1429 0.215 4(First Face of Second Lens) −4.4440 0.310 1.531 56.0 5(Second Face of Second Lens) 0.0000 (Image Surface) Face Number k A B C D 2 0 −3.61 2.13E+2 −9.43E+3 2.00E+5 3 0 −2.90 −4.85E+1 −4.11E+2 2.10E+4 4 0 −3.69 −3.41E+2 1.40E+4 −3.71E+5 5 0 −2.36 9.52 −2.12E+2 1.89E+3

Under such conditions, r₁/r₂=0.078 was achieved, thereby satisfying the expression (1). f₁/FL=0.919 was achieved, thereby satisfying the expression (2). d₃/FL=0.26 was achieved, thereby satisfying the expression (3) r₁/FL=0.459 was achieved, thereby satisfying the expression (4). d₂/d₁=0.72 was achieved, thereby satisfying the expression (5). d₂/d₃=0.69 was achieved, thereby satisfying the expression (6). d₁/FL=0.25 was achieved, thereby satisfying the expression (7). L/FL=1.132 was achieved, thereby satisfying the expression (8).

FIG. 35 shows the astigmatism and distortion of the imaging lens 1 of the SEVENTEENTH EXAMPLE.

According to the result, each of the astigmatism and distortion was almost satisfied. It can be seen from the result that a sufficient optical property can be obtained.

Eighteenth Example

FIG. 36 shows a EIGHTEENTH EXAMPLE of the present invention. In the EIGHTEENTH EXAMPLE, a surface apex and surrounding area of a first face 3 a of the first lens 3 passes through the diaphragm 2 and is positioned closest to the object side.

The imaging lens 1 of the EIGHTEENTH EXAMPLE was set under the following condition.

Lens Data L = 1.36 mm, FL = 1.19 mm, f₁ = 1.102 mm, f₂ = −8.846 mm, Fno = 2.8 Face Number r d nd νd (Object Point) 1(Diaphragm) ∞ −0.030 2(First Face of First Lens) 0.55 0.300 1.531 56.0 3(Second Face of First Lens) 7.00 0.215 4(First Face of Second Lens) −4.50 0.310 1.531 56.0 5(Second Face of Second Lens) −100.00 (Image Surface) Face Number k A B C D 2 0 −3.61 2.13E+2 −9.43E+3 2.00E+5 3 0 −2.90 −4.85E+1 −4.11E+2 2.10E+4 4 0 −3.69 −3.41E+2 1.40E+4 −3.71E+5 5 0 −2.36 9.52 −2.12E+2 1.89E+3

Under such conditions, r₁/r₂=0.079 was achieved, thereby satisfying the expression (1). f₁/FL=0.926 was achieved, thereby satisfying the expression (2). d₃/FL=0.26 was achieved, thereby satisfying the expression (3). r₁/FL=0.462 was achieved, thereby satisfying the expression (4). d₂/d₁=0.72 was achieved, thereby satisfying the expression (5). d₂/d₃=0.69 was achieved, thereby satisfying the expression (6). d₁/FL=0.25 was achieved, thereby satisfying the expression (7). L/FL=1.143 was achieved, thereby satisfying the expression (8).

FIG. 37 shows the astigmatism and distortion of the imaging lens 1 of the EIGHTEENTH EXAMPLE.

According to the result, each of the astigmatism and distortion was almost satisfied. It can be seen from the result that a sufficient optical property can be obtained.

The present invention is not limited to the above-described embodiments and EXAMPLES, and various modifications are possible as required. 

1. An imaging lens used for forming an image of an object on an image-taking surface of an solid image pickup element, consisting of: in order from an object side to an image surface side, a diaphragm, a first lens that is a lens having a positive power whose convex surface faces the object side, and a second lens that is a lens having a negative power whose concave surface faces the object side, wherein a condition expressed by the following expressions (1) to (3) are to be satisfied: −0.1≦r ₁ /r ₂<0.1  (1) 0.85≦f ₁ /FL≦1  (2) 0.1≦d ₃ /FL≦0.3  (3) where, r₁: center radius curvature of the object side face of the first lens r₂: center radius curvature of the image surface side face of the first lens f₁:focal distance of the first lens d₃: center thickness of the second lens FL: focal distance of the entire lens system.
 2. The imaging lens according to claim 1, wherein, further, a condition expressed by a following expression (4) is to be satisfied: 45≦r ₁ /FL≦0.53  (4).
 3. The imaging lens according to claim 1, wherein, further, a condition expressed by a following expression (5) is to be satisfied: 65≦d ₂ /d ₁≦1.25  (5) where, d₁: center thickness of the first lens d₂: distance between the first lens and the second lens on the optical axis.
 4. The imaging lens according to claim 1, wherein, further, a condition expressed by a following expression (6) is to be satisfied: 65≦d ₂ /d ₃≦1.1  (6) where, d₂: distance between the first lens and the second lens on the optical axis.
 5. In an imaging lens according to claim 1, a condition expressed by a following expression (7) is further satisfied: 0.1≦d ₁ /FL≦0.3  (7) where, d₁: center thickness of the first lens.
 6. The imaging lens according to claim 1, wherein, further, a condition expressed by a following expression (8) is further satisfied: 0.9≦L/FL≦1.2  (8) where, L: entire length of the lens system (distance from the surface positioned closest to the object side to the image taking surface on the optical axis [air reduced length]). 